How can I add growl to my MTD Grendel?

I have an MTD Grendel 5-string which I have really enjoyed playing. It has very nice balance and I have fallen in love with the 35" scale assymetric neck.

However, shortly after I bought it, I played an MTD Kingston and loved the growl that bass produced. I have since enjoyed the sound of MM bases. Just last week I listened to an excellent bass player on a cruise. His bass was tight punchy and had a mild growl in the midrange. I talked to him after the show and he showed me his Warwick Streamer Stage II (5). I loved the sound of this bass also, but I'm wondering if there is a way to get that sound from my Grendel.

Some information: I play 100% fingerstyle and play some mellow and some more alternative rock music. I usually play with mostly the neck jazz PU and use very little of the bridge PU. Since I don't use the bridge PU very much I was considering replacing it with something that I could blend in some of that growly tone I'm looking for. I thought about a basslines jazz pickup, but also considered routing out the top and adding a large coil MM style bridge pickup.

I'm surprised you aren't getting growl out of your Grendel - I had several MTD Beasts (passive 4-string Czech MTDs similar to your Grendel) and I think that growl was one of their main attributes (growly and punchy are the two words I'd use to characterize them).

When you favor the bridge pickup - does that not give you some growl? (I always favored the neck pickup slightly but it still growled). Also, the Grendel is active, right? Isn't it 2-band? Maybe try backing off the highs and lows some (bump the volume if needed) to bring out more midrange.